March 2005 - Haskell - Haskell.org

DALT 2005 deadline extension: 18 March
by baldoni 10 Mar '05

10 Mar '05

>>>> PLEASE ACCEPT OUR APOLOGIES IF YOU RECEIVE MULTIPLE COPIES <<<< Dear Colleague, Due to a large number of requests, we have extended the submission deadline for DALT 2005, the 3rd International Workshop on Declarative Agent Languages and Technologies to be held as part of the workshop programme of AAMAS in Utrecht in July, to *18 March 2005*. However, we would be grateful if you could register your paper as soon as possible to help us with the organisation of the reviewing process. For further details, please go to http://www.doc.ic.ac.uk/~ue/DALT-2005/ Best regards, Matteo, Ulle, Andrea, and Paolo -- Dr. Matteo Baldoni Dipartimento di Informatica | Universita` degli Studi di Torino | Tel. +39 011 6706756 C.so Svizzera, 185 | Fax. +39 011 751603 I-10149 Torino (Italy) | URL http://www.di.unito.it/~baldoni ----------------------------------------------------------------------- Please avoid sending me Word or PowerPoint attachments. See http://www.gnu.org/philosophy/no-word-attachments.html -----------------------------------------------------------------------

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Binary Tree Traversal.
by Paul Chen 10 Mar '05

10 Mar '05

data BinTree a = Nil | Node a (BinTree a) (BinTree a) inorder2 :: BinTree a -> [a] -> [a] inorder2 Nil xs = [] inorder2 (Node val b1 b2) xs = (inorder2 b1 (val:(inorder2 b2 (xs)))) I want to be able to traverse across the binary tree in order and that is what I have so far. But somehow it always return []. it seems to ignore the "val:" Y. C.

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client-side web scripting in Haskell?
by Dean Herington 09 Mar '05

09 Mar '05

Is there any practical way to do client-side web scripting in Haskell? All the references I have found to HaskellScript seem quite out of date. Dean

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GHCi and MAC
by Jimtopia . 09 Mar '05

09 Mar '05

Hi I am trying to use GHCi for the first time and can't figure out where to put/ how to open and use a module I have created If anyone can explain it would be much appriciated. Regards Jimmy

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VLHCC'05 (Visual Languages and Formal Methods) - Paper deadline extended to 30 March (Visual Languages and Formal Methods)
by Andy Schürr 08 Mar '05

08 Mar '05

Dear Colleagues, the combination of visual languages and formal methods is one of the traditional main topics of the IEEE VL/HCC conference series with a history of more than 20 years! It is still time to write a submission for this year's event (and to book a flight to Dallas ... ). Hope to see you in Dallas later this year! Andy Schürr ----------------------------------------------------- CALL FOR PAPERS 2005 IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC'05) Dallas, Texas, USA, 21-24 September 2005 *************************************************** * New Deadline of Paper Submission: 30 March 2005 * *************************************************** http://viscomp.utdallas.edu/vlhcc05/ ------------------------------------------------------ | KEYNOTE SPEAKERS: | | | | Allen Cypher, IBM Almaden Research Center | | Henry Fuchs, Univ. of North Carolina - Chapel Hill | ------------------------------------------------------ Visual languages (VLs) have long been a means of effective communication between human and machine. Today, they are successfully employed for end-user programming, modeling, rapid prototyping, and design activities by people of many disciplines including architects, artists, children, engineers, and scientists. In addition, visual languages and technologies are increasingly being used to facilitate human-human communication through the Internet Web technology, and electronic mobile devices. The IEEE Symposium on Visual Languages and Human-Centric Computing (VL/HCC) is the premier international forum for researchers and industrial practitioners to discuss the state-of-the-art in visual languages and their applications. This year, VL/HCC'05 together with several satellite events will be held in Dallas, Texas, USA, in the heart of the complex of over 600 major multinational technology corporations known as the Telecom Corridor. SCOPE AND TOPICS We solicit original, unpublished research papers that focus on some aspect of visual language or human-centric computing technology, whether it be visual technology, text, sound, taste, virtual reality, the Web, or other multimedia technologies. Research papers may address cognitive and design aspects, underlying theories, taxonomies, implementation work, tool support, and case studies. Topics of interest include but are not limited to the following: * End-User and Domain-Specific Languages * Empirical Studies of Visual Languages and End-User Programming * Human-Centric Software Development * Multimedia Authoring Languages * Multi-Modal Interaction * Software Visualization and Animation * Theory of Visual Languages * Visual Languages for Design * Visual Languages for Education * Visual Languages in Software Engineering * Visual Modeling and Specification Languages * Visual Programming Environments * Visual Query Languages and Databases * Visual Techniques for Business Processes and Workflow STUDENT EVENT VL/HCC is anticipating a fully funded graduate student consortium for graduate students working on research relevant to VL/HCC. As in prior years, funding to provide transportation, housing, and registration for graduate student participants is anticipated. The application process details should be similar to that of prior years; details will become available later this year. PAPER SUBMISSION Submissions that address research and development, as well as experience reports and tool demonstration proposals on the above and other related topics are strongly encouraged. All the submitted papers will be reviewed by the international Program Committee members. Accepted papers will be published in the Proceedings of VL/HCC'05 by the IEEE Computer Society. A selection of the best papers will be invited for subsequent publication in a special issue of the Journal of Visual Languages and Computing. Research papers and experience reports of up to eight (8) and tool demonstrations of up to two (2) IEEE double-column pages should be submitted electronically. Detailed information on electronic submission can be found at the VL/HCC'05 Web site: http://viscomp.utdallas.edu/vlhcc05. IMPORTANT DATES Paper submission: 30 March 2005 Notification of decision: 22 May 2005 Camera-ready copy: 19 June 2005 GENERAL CO-CHAIRS Allen Ambler, University of Kansas, USA Kang Zhang, University of Texas at Dallas, USA PROGRAM CO-CHAIRS Martin Erwig, Oregon State University, USA Andy Schuerr, Darmstadt University of Technology, Germany PUBLICITY CHAIR Chris Hundhausen, Washington State University, USA FINANCE CHAIR Jing Dong, University of Texas at Dallas, USA TUTORIAL/WORKSHOP CHAIR Mark Minas, University of the Federal Armed Forces, Germany LOCAL CHAIR Kendra Cooper, University of Texas at Dallas, USA PROGRAM COMMITTEE Thomas Baar, Ecole Polytechnique Federale de Lausanne, Switzerland Alan Blackwell, University of Cambdridge, UK Adam Borkowski, Institute of Fundamental Technological Research, Poland Paolo Bottoni, Universita di Roma, Italy Margaret Burnett, Oregon State University, USA Shi-Kuo Chang, University of Pittsburgh, USA Maria Francesca Costabile, Universita di Bari, Italy Gennaro Costagliola, Universita di Salerno, Italy Phil Cox, Dalhousie University, Canada Isabel Cruz, University of Illinois at Chicago, USA Gregor Engels, Universitaet Paderborn, Germany Mark Gross, Carnegie Mellon University, USA John Hosking, University of Auckland, New Zealand John Howse, University of Brighton, UK Chris Hundhausen, Washington State University, USA Gabor Karsai, Vanderbilt University, USA Stefano Levialdi, Universita di Roma, IT Mark Minas, Universitaet der Bundeswehr in Muenchen, Germany Pierre-Alain Muller, Universite de Haute Alsace, France Marc Najork, Microsoft, USA Noritaka Osawa, National Institute of Multimedia Education, Japan Emmanuel Pietriga, INRIA, France Steve Reiss, Brown University, USA Mary Beth Rosson, Pennsylvania State University, USA Nenad Stankovic, Nanyang Technological University, Singapore Shin Takahashi, University of Tsukuba, Japan Steve Tanimoto, University of Washington, USA Juha-Pekka Tolvanen, MetaCase, Finland Susan Wiedenbeck, Drexel University, USA Guido Wirtz, Universitaet Bamberg, Germany WEB MASTERS Jun Kong, Guanglei Song, University of Texas at Dallas CONTACT Kang Zhang Visual Computing Lab, Dept of Computer Science University of Texas at Dallas Richardson, TX 75083-0688, USA Tel: +1-972-8836351 (direct) Fax: +1-972-8832349 (dept.) Email: vlhcc05(a)utdallas.edu http://viscomp.utdallas.edu/vlhcc05/

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Compiling GHC on Panther using darwin ports
by Chris Brown 08 Mar '05

08 Mar '05

Hi, I am trying to install GHC on Mac OS X (Panther) using Darwin Ports. When i run sudo port install ghc I get the following error message shortly into the compilation: ------------------------------------------------------------------------ ==fptools== make boot - --no-print-directory -r; in /Users/chrisbrown/darwinports/dports/lang/ghc/work/ghc-6.2.2/ghc/utils/ hasktags ------------------------------------------------------------------------ /Users/chrisbrown/darwinports/dports/lang/ghc/work/ghc-bootstrap/bin/ ghc -M -optdep-f -optdep.depend -osuf o -H16m -O -I/opt/local/include -L/opt/local/lib HaskTags.hs dyld: /Users/chrisbrown/darwinports/dports/lang/ghc/work/ghc-bootstrap/lib/ ghc-6.2.2/ghc-6.2.2 can't open library: /opt/local/lib/libdl.1.dylib (No such file or directory, errno = 2) make[3]: *** [depend] Trace/BPT trap make[2]: *** [boot] Error 1 make[1]: *** [boot] Error 1 make: *** [build] Error 1 I remember on Tiger this was because the portfile which tells darwin ports what to do has a condition in it to compile the bootstrap differently for panther or jaguar (and obviously not tiger). Could anyone please help me to fix this compilation error? Thanks, Chris Brown.

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"Classic" vs. "Cunning Newtype" Derivation
by Ashley Yakeley 07 Mar '05

07 Mar '05

I make quite a lot of use of "cunning newtype" deriviation (in GHC), because it's easy to understand. newtype Mytype = MkMytype T deriving C However, if I use one of the standard derivable classes (Eq, Ord, Enum, Bounded, Show, and Read), I believe that form of deriving takes priority. AFAICT from the H98 Report ch. 10, for Eq, Ord and Bounded this works out as the same thing, Enum doesn't apply, and Read and Show do something different. Is this correct, or are there subtle differences? -- Ashley Yakeley, Seattle WA

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Hierarchical module namespace extension not sufficiently flexible
by Duncan Coutts 07 Mar '05

07 Mar '05

All, So here's the problem: we have a binding to a large foreign library (GTK) which we are trying to fit nicely into hierarchical module name space. It would live under Graphics.UI.Gtk Graphics.UI.Gtk.Button Graphics.UI.Gtk.Frame ... etc Now there are over 100 modules directly under Graphics.UI.Gtk and you don't want to have to import each one of them separately. Of course you will not use all of them in one module but you might reasonably use 20+ of them. So it'd be nice to be able to say: > import Graphics.UI.Gtk or > import qualified Graphics.UI.Gtk as Gtk But now we have a problem. These import directives import a flat namespace, or a flat namespace qualified by a single module alias (ie Gtk in the second example). But the Gtk modules are deliberatly designed to have hierarchical names. You cannot simply combine them all together into a flat namespace without falling back to the trick of prefixing each function name with the module name. So while we would like to be able for users to do this: > import Graphics.UI.Gtk > > ... Button.setLabel ... They will instead have to say: > import Graphics.UI.Gtk > > ... buttonSetLabel ... Which is one of the things that the hierarchical module namespace extension was trying to get rid of! All the other language bindings for Gtk (apart from C) use the former import and useage style. It doesn't make us look good! :-) So my question is: have I overlooked something or is this really not possible at the moment. And secondly, if it is currently not possible is there a 'nice' extension that would allow this sort of thing. (Where nice probably means Haskell98 compatible / 'doesn't' break existing programs) How about: > module Graphics.UI.Gtk ( > > module qualified Graphics.UI.Gtk.Button as Button > ... > ) where > > import Graphics.UI.Gtk.Button or equivalently(?): > module Graphics.UI.Gtk ( > > module qualified Button > ... > ) where > > import Graphics.UI.Gtk.Button as Button Duncan Ps there's a oddity I found where if you say: > module Foo ( > module Bar > ) > > import qualified Bar then module Foo exports precisely nothing. But there's no error or warning.

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LPNMR'05: Call for Papers
by lpnmr05.publicity＠mat.unical.it 07 Mar '05

07 Mar '05

[Apologies if you receive this more than once] Call for Papers 8th International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR'05) Diamante, Cosenza, Italy September 5-8, 2005 http://www.mat.unical.it/lpnmr05/ LPNMR'05 is the eighth in the series of international meetings on logic programming and nonmonotonic reasoning. Seven previous meetings were held in Washington, D.C., (1991), in Lisbon, Portugal (1993), in Lexington, Kentucky (1995), in Dagstuhl, Germany (1997), in El Paso, Texas (1999), in Vienna, Austria (2001), and in Fort Lauderdale, Florida (2004). LPNMR'05 will be organized by the Department of Mathematics of University of Calabria (Italy), and will be co-located with the INFOMIX Workshop on Data Integration. AIMS AND SCOPE -------------- LPNMR is a forum for exchanging ideas on declarative logic programming, nonmonotonic reasoning and knowledge representation. The aim of the conference is to facilitate interactions between researchers interested in the design and implementation of logic based programming languages and database systems, and researchers who work in the areas of knowledge representation and nonmonotonic reasoning. LPNMR strives to encompass these theoretical and exprimental studies that lead to the construction of practical systems for declarative programming and knowledge representation. Authors are invited to submit papers presenting original and unpublished research on nonmonotonic aspects of logic programming and knowledge representation. We particularly encourage papers on application of LPNMR techniques to build significant applications. A non-exhaustive list of topics of interest includes: 1. Development and mathematical studies of logical systems with nonmonotonic entailment relations: - Semantics of new and existing languages; - Relationships between formalisms; - Complexity and expressive power; - Development of inference algorithms and search heuristics for LPNMR systems; - Extensions of ''classical'' LPNMR languages by new logical connectives and new inference capabilities such as abduction, reasoning by cases, etc; - Updates and other operations on LPNMR systems; - Uncertainty in LPNMR systems. 2. Implementation of LPNMR systems: - system descriptions, comparisons, evaluations; - LPNMR benchmarks. 3. Applications of LPNMR systems: - LPNMR languages and algorithms in planning, diagnosis, software engineering, decision making, and other domains; - Applications of LPNMR languages in Data Integration and Exchange systems; - Methodology of representing knowledge in LPNMR languages: theory and practice; - Integration of LPNMR systems with other computational paradigms; - Embedded LPNMR systems: Systems using LPNMR subsystems. SYSTEM AND APPLICATION DEMONSTRATION TRACKS ------------------------------------------- As part of the technical program, we also plan a special session devoted to presentations and demonstrations of implemented nonmonotonic reasoning systems. Systems and application demonstration tracks will be announced in a distinct call. IMPORTANT DATES --------------- Abstract Submission Deadline March 22, 2005, 23:59:59 GMT Paper Submission Deadline March 25, 2005, 23:59:59 GMT Notification (Accept/Reject) May 16, 2005 Conference Schedule June 6, 2005 Final Conference Papers June 10, 2005 Early Registration Deadline July 4, 2005 Conference September 5-8, 2005 SUBMISSION OF PAPERS -------------------- Papers must not exceed thirteen (13) pages including title page, references and figures, and must be formatted according to the Springer LNCS/LNAI authors' instructions (see <URL:http://www.springer.de/comp/lncs/authors.html>). Papers must be written in English and present original research. Paper submission is electronic via the conference home page http://www.mat.unical.it/lpnmr05/. Papers must be registered (title, abstract, keywords, authors, contact information) by March 22, 2005, 23:59:59 GMT; the full paper must be uploaded by March 25, 2005, 23:59:59 GMT. PROGRAM CO-CHAIRS ----------------- Chitta Baral (Arizona State University, USA) Nicola Leone (University of Calabria, Italy) PROGRAM COMMITTEE ----------------- Jose Alferes (New University of Lisbon, Portugal) Leopoldo Bertossi (Carleton University, Canada) Pedro Cabalar (Corunna University, Spain) Gerhard Brewka (Leipzig University, Germany) Juergen Dix (Technical University of Clausthal, Germany) Wolfgang Faber (University of Calabria, Italy) Norman Foo (National ICT Australia and University of New South Wales, Australia) Michael Gelfond (Texas Tech University, USA) Antonis Kakas (University of Cyprus, Cyprus) Katsumi Inoue (National Institute of Informatics, Japan) Vladimir Lifschitz (University of Texas at Austin, USA) Fangzhen Lin (Hong Kong University of Science and Technology, China) Ilkka Niemelä (Helsinki University of Technology, Finland) David Pearce (Rey Juan Carlos University, Spain) Alessandro Provetti (University of Messina, Italy) Francesco Scarcello (University of Calabria, Italy) Torsten Schaub (University of Potsdam, Germany) Hans Tompits (Vienna University of Technology, Austria) Francesca Toni (Imperial College, London, UK) Mirek Truszczynski (University of Kentucky, USA) Marina de Vos (University of Bath, United Kingdom) PUBLICITY CHAIR --------------- Gianluigi Greco (University of Calabria, Italy) LOCAL ORGANIZATION CO-CHAIRS ---------------------------- Giovambattista Ianni (University of Calabria, Italy) Giorgio Terracina (University of Calabria, Italy)

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Proposal: Allow "\=" for field update in record update syntax
by S. Alexander Jacobson 05 Mar '05

05 Mar '05

I don't know what it takes to get this sort of change into circulation, but I assume it starts with a clear and specific description of the problem, exploration of alternatives, and a specific proposed solution. So here goes: ---------- Proposal: Allow "\=" for field update in record update syntax Specifically, intepret rec {field\=fn} as rec {field = fn (field rec)} Jusitification: It is extremely common when updating records to be updating a field value based on its prior value rather than simply assigning a new value from nothing. Unforunately the syntax supports the later clearly but makes the former awkward to read, understand, and debug: myFun db myType1 = db { tMyType1 = insert myType1 $ tMyType1 db nextId = 1 + (nextId db) } One solution to this problem that does not involve changing syntax is to generate field update functions for every field of a type e.g.: update_tMyType1 f s = s {tMyType1= f $ myType1 s} update_nextId f s = s {nextId = f $ nextId s} Once you have those functions, myFun looks much better: myFun db myType = update_nextId (+1) $ update_tMyType1 f db where f= insert myType1 But, generating the update_ functions is not programming; its just manual syntax generation. And, even if you have template haskell to do it, * it is annoying to have to find/write the TH code to implement * update_ is incredibly verbose * shortening it risks proliferation of psuedo-syntax: u_tMyType, u__tMyType, or utMyType? * it adds clutter to have to call the TH for each record type, and * it pollutes the name space/increases risk of name collision Rather than force the user to jump through these hoops, why not make the syntax flow naturally from the existing record update syntax? It makes sense to use \= for this task as it is the functional generalization of C or Java's += or *= . Then myFun would have the elegant and clear syntax: myFun db myType1 =db {tMyType1\=insert myType1, nextId\=(+1)} -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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